Explosive shells made iron hulls inevitable

Did cast-iron framing make the Royal Navy's shift to all-metal ships inevitable?

The decisive pressure was explosive shellfire, which made wooden hulls increasingly untenable for every major navy.

Wooden hulls were naturally buoyant and could remain afloat after absorbing older solid-shot damage. Explosive shells changed the problem by detonating inside, blowing the structure apart from within and producing effects compared here to a magazine explosion. Navies therefore needed stronger hull materials and armor that prevented shells from entering in the first place. The shift was not uniquely forced by British cast-iron framing; explosive ordnance made some form of metal construction and protection increasingly necessary across the major navies.